1. Field of the Invention
The present invention relates to optical communication equipment and, more specifically, to reducing effects of chromatic dispersion (CD).
2. Description of the Related Art
Chromatic dispersion (CD) occurs in an optical fiber as a result of the variation of the index of refraction with wavelength. Due to chromatic dispersion, different spectral components of an optical signal travel in a fiber at different speeds and arrive at the receiver with a group delay. As a result, optical pulses corresponding to optical bits may be significantly distorted and cause errors at the receiver. Chromatic dispersion is well known to severely impair transmission of optical signals at relatively high bit rates (e.g., 40 Gb/s) over relatively large distances (e.g., 1000 km).
Several techniques have been proposed to date to mitigate the effects of chromatic dispersion in optical communication systems. Typically, a device known as a dispersion compensator is deployed at the receiver end of a fiber transmission link to improve the chances that the receiver correctly decodes CD-distorted optical bits. One approach to designing a dispersion compensator is to use one or more gratings for signal processing. During such processing, an optical signal is spectrally decomposed into the corresponding beams that are then routed along different optical paths to generate group delay. Disadvantageously however, in prior art dispersion compensators, the delayed beams arriving at the output of the compensator are typically spatially separated and/or directionally diverse. As a result, prior art dispersion compensators induce optical signal losses that are non-uniform over the bandwidth of a typical optical communication channel. This non-uniformity may cause additional distortion of optical pulses and further errors at the receiver.